Re: [Qemu-devel] [PATCH v2] mirror: follow AioContext change gracefully

[Stefan Hajnoczi <stefanha@redhat.com>]

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On Sun, Jun 12, 2016 at 02:51:04PM +0800, Fam Zheng wrote:
> From: Stefan Hajnoczi <stefanha@redhat.com>
> 
> When dataplane is enabled or disabled the drive switches to a new
> AioContext.  The mirror block job must also move to the new AioContext
> so that drive accesses are always made within its AioContext.
> 
> This patch partially achieves that by draining target and source
> requests to reach a quiescent point.  The job is resumed in the new
> AioContext after moving s->target into the new AioContext.
> 
> The quiesce_requested flag is added to deal with yield points in
> block_job_sleep_ns(), bdrv_is_allocated_above(), and
> bdrv_get_block_status_above().  Previously they continue executing in
> the old AioContext. The nested aio_poll in mirror_detach_aio_context
> will drive the mirror coroutine upto fixed yield points, where
> mirror_check_for_quiesce is called.
> 
> Cc: Fam Zheng <famz@redhat.com>
> Cc: Paolo Bonzini <pbonzini@redhat.com>
> Cc: Jeff Cody <jcody@redhat.com>
> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
> [Drain source as well, and add s->quiesce_requested flag. -- Fam]
> Signed-off-by: Fam Zheng <famz@redhat.com>
> 
> ---
> 
> v2: Picked up Stefan's RFC patch and move on towards a more complete
> fix.  Please review!

Thanks, I'll send a v3 with my own comment addressed and fixes for other
block jobs.

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